Erectile dysfunction (ED) affects ~ 50% of men aged 40 to 70 and has a high impact on men's health and quality of life. Current treatments are ineffective in the difficult to treat prostatectomy (16-82%) and diabetic (56-59%) patients due to injury to the cavernous nerve (CN), which provides innervation to the penis. With denervation the critical smooth muscle (SM) undergoes apoptosis and the penis becomes fibrotic, with increased collagen and a change in subtypes, thus altering the architecture of the corpora cavernosa. This application is significant because we propose a novel integrative approach that targets the 3 main morphological changes that underlie ED, which are CN degeneration, SM apoptosis, and penile fibrosis. The sonic hedgehog (SHH) pathway is critical for the response of the penis to denervation. CN injury decreases SHH in the penis, which causes SM apoptosis and ED. CN injury also decreases SHH in the CN (70%), which causes demyelination and axonal degeneration of CN fibers. We are developing two novel and innovative peptide amphiphile (PA) nanofiber hydrogels for delivery of SHH protein to the CN and to the penis to promote regeneration and prevent penile apoptosis. Our preliminary results show accelerated CN regeneration, ~60% improved erectile function (6 weeks) and suppressed penile apoptosis in response to SHH PA treatment of the CN. When a second type of PA for SHH was injected into the penis of CN injured rats, apoptosis was suppressed 25%. These innovative studies are highly promising that optimization of PA methodology, SHH concentration and delivery (Aim 1 and 2), will even further enhance regeneration of CN and penile morphology and function. The SHH PA is highly translatable for treatment of prostatectomy and diabetic patients by substituting human SHH protein for rat. SM/endothelial interaction is critical to maintain penile architecture and only one factor has been identified in both, which is hedgehog interacting protein (HIP, SHH target). Hip is synthesized in SM and HIP protein is localized in SM and endothelium, suggesting that HIP plays a role in communication between the cell types. HIP is also synthesized in pelvic ganglia (PG) neurons, and is the only protein known to undergo anterograde transport by the CN. HIP transport has not been found in any other organ. Since HIP inhibition causes more profound axonal degeneration than SHH, it has significant regenerative potential and offers a unique opportunity to study the nerve/SM/endothelial interface that is not possible in other organs (Aim 3). As SM is lost, increased collagen occurs in prostatectomy patients by a largely unknown mechanism. SHH has been suggested to play a role in renal and pulmonary fibrosis and altered collagen production. We show that SHH suppresses collagen induction in response to CN injury and propose that SHH is a regulator of collagen in the penis (Aim 4). This is an innovative idea with significant potential for interventin and suggests that the SHH pathway sits at the nexus of several key pathways which regulate erectile function.